1. Field of the Invention
The present invention relates to windshield wipers, and in particular, windshield wipers with variable arm pressure.
2. Description of the Related Art
In recent years, there has been a strong requirement for reducing the noise which results during windshield wiper operation when the windshield glass is struck by the blade as the wiper reverses direction. As shown in FIG. 7, this reversal noise is related to the pressure exerted by the tip of the wiper arm (arm pressure); the higher the arm pressure, the louder the reversal noise. Thus, reducing the arm pressure at the points where the wiper reverses direction would decrease the reversal noise.
A variable arm pressure windshield wiper device is disclosed in Japanese Patent Publication Sho 62-59151. That device utilizes motor operation via a link to change the position of the distal end of the spring's attachment point on the wiper arm in order to vary the pressure on the arm.
However, in the device disclosed in the referenced Japanese Publication, the reversal point of the wiper arm must be detected in order to operate the motor. This arrangement is not advantageous in that response time is poor, reliability is low, and the complexity of the device is relatively high.